This application claims the priority of Korean Patent Application No. 2003-81098 filed on Nov. 17, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an apparatus for ionized physical vapor deposition, and more particularly, to an apparatus for ionized physical vapor deposition using a helical self-resonant coil.
2. Description of the Related Art
Various types of systems for wafer fine processing for manufacturing a semiconductor device and flat display panel have been used. Amongst them, a physical vapor deposition (PVD) system is one of the most widely used for depositing a predetermined material film on a surface of a wafer for manufacturing a semiconductor device or a flat display panel. Examples of the PVD system include a magnetron sputtering apparatus, an E-beam evaporator system, and a thermal evaporator system.
In the conventional PVD system, a majority of particles, such as atoms or atomic clusters, ejected from a target material and being deposited on a substrate are neutral in charge. Therefore, a structure of the particles deposited on the substrate is not dense resulting in a poor qualify of deposited thin film and a surface of a thin film is not planarized. In order to solve this problem, a method of heating the substrate to a predetermined temperature has been tried, but heating the substrate can not be an appropriate solution when the substrate is formed of a material such as glass, having low resistance to heat.
In order to improve these drawbacks of the conventional PVD system, an ionized physical vapor deposition (IPVD) system has been developed. The IPVD system is configured to ionize particles ejected from a target material using plasma and to accelerate the ions by applying a bias voltage to the substrate. Accordingly, the IPVD system is known to have the advantage of providing a thin film having superior film quality and planarization.
FIG. 1 shows a schematic diagram of a magnetron sputtering apparatus depicted in U.S. Pat. No. 6,117,279 as an example of a conventional IPVD apparatus.
Referring to FIG. 1, the conventional magnetron sputtering apparatus has a vacuum chamber 12 that surrounds a plasma processing space 11. A substrate holder 14 for supporting a wafer 15 is mounted in a lower part of the vacuum chamber 12, and a cathode assembly 17 is mounted on an upper part of the vacuum chamber 12. The inside of the vacuum chamber 12 is maintained in a predetermined vacuum state by a vacuum pump 39. A process gas is supplied into the vacuum chamber 12 from a process gas source 40 through a flow control device 41. The cathode assembly 17 consists of magnets 76, a target 16 formed of a deposition material, and a target holder 18 wherein the target 16 is disposed facing the wafer 15 at a predetermined distance. A DC power source 21 for applying an electrical energy to the target 16 is connected to the cathode assembly 17 through an RF filter 22. An optional RF power source 24 is connected to the cathode assembly 17 through a matching network 25. Also, a bias power source 27 for supplying power to the wafer 15 is provided and connected to the substrate holder 14 through a matching network 28.
An RF coil 30 is wound around the vacuum chamber 12, and an RF power source 32 for supplying energy to the coil 30 is connected to the RF coil 30 via a matching network 33. The RF coil 30 generates inductively coupled plasma by supplying power to an upper space 26 of the vacuum chamber 12. The plasma produced ionizes the deposition material particles sputtered from the target 16. The ionized deposition material particles are accelerated toward the wafer 15 to which a bias energy is applied, and form a superior quality of a thin film on the surface of the wafer 15.
A dielectric window 60 for tight sealing with the upper space 26 of the vacuum chamber 12 where plasma is generated is mounted inside of the RF coil 30. A shield 70 to prevent a surface of the dielectric window 60 from coating build-up of the deposition material sputtered from the target 16 is mounted between the dielectric window 60 and the space 26.
A conventional IPVD apparatus having an above mentioned structure uses inductively coupled plasma generated by an RF coil, i.e., a non-resonant coil for ionization of the deposition material. However, the non-resonant coil can ignite plasma at a pressure range from 1 mTorr to a few tens mTorr, but it hardly can ignite plasma at a lower pressure than this range. Also, there is a disadvantage in that an ionization rate of the deposition material by the plasma produced by the RF coil is not satisfactory since the non-resonant coil has a certain limit to produce high-density plasma.
U.S. Pat. No. 5,903,106 discloses a plasma generating apparatus having an electrostatic shield. The electrostatic shield for controlling electromagnetic energy coupled to the plasma has a plurality of openings therethrough. However, when this configuration of electrostatic shield is applied to the IPVD apparatus, the deposition material may be sputtered to the coil that surrounds the electrostatic shield or a material for forming the coil may be sputtered on the substrate through the openings.
According to the foregoing aspects, a core technique that should be developed for the IPVD apparatus is a plasma source able to generate high density plasma even at very low pressure.